under the Köppen system due to summer heat instead of the length of the growing season being the trigger for Köppen.

In boreal/subpolar areas, Trewartha defines areas like Anchorage that have winters averaging over -10 C as oceanic climates even if they are insufficiently mild to be classified as oceanic under Köppen too like Reykjavík is, as opposed to the freezing isotherm used in temperate climates. Nonetheless, Köppen and Trewartha concur on the summer